Everything I read (and I always say this so people understand that I’m not pretending to be an expert but I have done a lot of reading) says the absolute min for a adult is a 40gal tank but some suggest to go a bigger to make sure they have plenty of room and of course some beardies may be above average size. But beyond a looking at gallons check the length and width. There are 36” and 48” inch 40gal tanks. 36” tanks are taller. The longer one is the best option because they don’t need much vertical space since they are ground dwellers. It’s my understanding that they reach full size at 18mos-2yrs. So I’m sure you’re enclosure will be adequate for awhile. My best guess is that the demand for larger tanks isn’t high enough? I’ve seen some sites the build custom cages and I’ve watched one DIY build on YouTube but I don’t know if I have those skills. My beardie is still a juvenile and he’s in s 40 gal 36” tank. I will keep an eye out for something a bit bigger as he grows. I would have gone bigger but like you I couldn’t find many larger and for a good price.if that big why does no one sell a 60gal or bigger tank for bearded dragons
Probably because they are big, so they take up a lot of space,they are relatively expensive, depending on the style they are likely to be quite heavy so all in all not worth the hassle would be my guess why they are not readily available in "pet stores". I have seen some at reptile stores and also at other specialty pet stores that have reptiles available.if that big why does no one sell a 60gal or bigger tank for bearded dragons